Method of saving power of station in wireless network

ABSTRACT

A method of saving power of a station in wireless network is provided. The station comprises a connectivity module, a central processing unit, and peripheral devices. The method includes: upon receiving a wake-up signal, powering on the connectivity module, the central processing unit, and the peripheral devices; performing the central processing unit and the peripheral devices in a connection state; performing the connectivity module in an authenticated state; and upon a condition that there is no data to be transferred to the station or after the station transmits and receives all needed data, performing a sleep mode to power off the connectivity module, the central processing unit, and the peripheral devices.

CROSS REFERENCE TO RELATED APPLICATION

This is a Continuation Application of a U.S. patent application Ser. No.14/846,270, filed on Sep. 4, 2015. The disclosures of the above-listedapplication are hereby incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to communication, and more specifically toa method for saving power of a station in the wireless network.

2. Description of the Prior Art

Wireless networks are widely deployed to provide various communicationservices such as video, voice, broadcast, messaging, etc. These wirelessnetworks may be capable of supporting communication for multiple usersby sharing the available network resources. Examples of such networksinclude wireless local area networks (WLANs), wireless metropolitan areanetworks (WMANs), wireless wide area networks (WWANs), and wirelesspersonal area networks (WPANs).

A wireless network may include any number of access points (APs) and anynumber of stations. An access point may act as a coordinator forcommunication with the stations. A station may actively communicate withan access point, may be idle, or may be powered down at any given momentdepending on the data requirements of the station.

For a station operating in a power saving mode, when no packet isreceived or transmitted (hereinafter referred to as a sleep period),components of the station are turned off to reduce current consumption.In order to receive a scheduled packet, components of the station arewakening up before the scheduled packet arrives. For example, during asleep period, most components, except a GPIO device, of the station areturned off to reduce current consumption.

Because current handheld stations, such as wireless handheld device, arepowered by batteries, power saving has always been the primary issueconcerned. Proper sleep periods help prolong powered time and batterylife.

IEEE 802.11 is a family of standards developed by The Institute ofElectrical and Electronics Engineers (IEEE) for WLANs. IEEE 802.11defines a method for a station to sleep and thus save power. However,the efficiency of the method is limited for stations desiring very lowpower consumption because of signaling limitations in the standard aswell as limited support by the access points and/or stations.

There is therefore a need in the art for techniques to improve the sleepperiod of a station in a wireless network.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method of savingpower of a station in wireless network by increasing the sleep period ofthe station.

According to the present invention, a method of saving power of astation in wireless network is provided. The station comprises aconnectivity module, a central processing unit (CPU), and peripheraldevices. The method comprises: upon receiving a wake-up signal, poweringon the connectivity module, the central processing unit, and theperipheral devices; performing the central processing unit and theperipheral devices in a connection state; performing the connectivitymodule in an authenticated state; and upon a condition that there is nodata to be transferred to the station or after the station transmits andreceives all needed data, performing a sleep mode to power off theconnectivity module, the central processing unit, and the peripheraldevices.

In one aspect of the present invention, the station further comprises ageneral purpose input/output (GPIO) device, and the wake-up signal issent from the GPIO device in response to an external event.

In another aspect of the present invention, the station furthercomprises a timer, the method further comprises: upon receiving thewake-up signal, powering on the timer; performing the timer in theconnection state; and upon the condition that there is no data to betransferred to the station or after the station transmits and receivesall needed data, performing the sleep mode to power off the timer.

In another aspect of the present invention, the method furthercomprises:

upon a condition that there is data to be transferred by checkingdelivery traffic indication message (DTIM) from an access point,performing the connectivity module in the authenticated state.

In another aspect of the present invention, the station furthercomprises a timer, and the wake-up signal is generated when the timerexpires by a predetermined time period.

In another aspect of the present invention, the predetermined timeperiod is longer than an interval between two delivery trafficindication messages from the access point.

In another aspect of the present invention, the station furthercomprises a retention memory for storing information relating toassociated states of the central processing unit, and the peripheraldevices, and relating to authenticated states of the connectivity modulein a previous operation occurred before the last sleep mode. The methodfurther comprises: performing the connectivity module in theauthenticated state complying with the previous operation.

In still another aspect of the present invention, the connectivitymodule comprises a modulator/demodulator, a radio frequency (RF)transceiver, an analog-to-digital converter, a digital-to-analogconverter, and a media access controller.

In yet another aspect of the present invention, the connectivity moduleof the station connects to another station by using WiFi, Bluetooth,Zigbee, and ZWAVE wireless technology standard.

In contrast to prior art, the present invention proposes that a wake upsignal is sent from the GPIO device in response to an external event oris periodically generated by the timer. Upon receiving the wake upsignal, the battery supplies power to power on the connectivity module,the central processing unit, and the peripheral devices. Since eitherthe interval of the wake up signal sent from the GPIO device in responseto the external event or the interval of the wake up signal periodicallygenerated by the timer is a few multiples of the DTIM intervals, thesleep period of the elements in the station 100 according to the presentinvention is longer than the conventional DTIM intervals. Therefore, thestation using the present invention may save more power and thus makethe battery life longer.

These and other objectives of the present invention will become apparentto those of ordinary skill in the art after reading the followingdetailed description of the preferred embodiment that is illustrated inthe various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system with an access point andmultiple stations according to the present invention.

FIG. 2 shows a block diagram of a station according to a preferredembodiment of the present invention.

FIG. 3 is a flowchart of a method of saving power of a station in awireless network according to a first embodiment of the presentinvention.

FIG. 4 illustrates a variety of power supply to the station of thepresent invention.

FIG. 5 illustrates a comparison of sleep/wake up modes betweenconventional technology and the present invention.

FIG. 6 is a flowchart of a method of saving power of a station in awireless network according to a second embodiment of the presentinvention.

FIG. 7 is a flowchart of a method of saving power of a station in awireless network according to a third embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The power saving techniques described herein may be used for variouswireless networks such as WLANs, WMANs, WWANs, WPANs, etc. A WLAN mayimplement a radio technology such as any defined by IEEE 802.11. A WWANmay be a cellular network such as a Code Division Multiple Access (CDMA)network, a Time Division Multiple Access (TDMA) network, a FrequencyDivision Multiple Access (FDMA) network, an Orthogonal FDMA (OFDMA)network, a Single-Carrier FDMA (SC-FDMA) network, etc. A WMAN mayimplement a radio technology such as any defined by IEEE 802.16 such as802.16e, which is commonly referred to as WiMAX, or IEEE 802.20. A WPANmay implement a radio technology such as Bluetooth. For clarity, thetechniques are described below for an IEEE 802.11 WLAN.

FIG. 1 shows a wireless communication system 10 with an access point(AP) 200 and multiple stations 100 according to the present invention.In general, a wireless network may include any number of access pointsand any number of stations. A station is a device that can communicatewith another station via a wireless channel. A station may communicatewith an access point or peer-to-peer with another station. A station maybe a mobile phone, a handheld device, a smart phone, a personal digitalassistant (PDA), a laptop computer, and so on. An access point is astation that provides access to distribution services via the wirelesschannel for stations associated with that access point. A station maycommunicate with an access point for one or more flows. A flow is ahigher layer data stream that is sent via a link. A flow may utilizeTransmission Control Protocol (TCP), User Datagram Protocol (UDP), orsome other protocol at a transport layer.

The invention can be implemented in a wireless communication system withpower saving mechanism, such as wireless local area network power savingspecified in the IEEE 802.11 standard. The stations operating in thepower saving mode listen to beacon frames periodically broadcast fromthe access point. If the station is informed by the beacon frame thatdata packets are buffered at the access point, it will send triggerframe to the access point for the queued data packets.

FIG. 2 shows a block diagram of a station 100 according to a preferredembodiment of the present invention. The station 100 comprises a generalpurpose input/output (GPIO) device 115, a timer 101, a connectivitymodule 140, a central processing unit (CPU) 110, a random access memory112 for the CPU 110, peripheral devices 114, a battery 130, and aretention memory 116. The connectivity module 140 is used for connectingto another station when powering on by using specific wirelesstechnology standards, such as WiFi, Bluetooth, Zigbee, and ZWAVE. Theconnectivity module 140 comprises a modulator/demodulator 102, a radiofrequency (RF) transceiver 104, an analog-to-digitalconverter/digital-to-analog converter 106, and a media access controller108. The peripheral devices 114 can be a Universal Serial Bus (USB)device, a screen, a keyboard, or a speaker.

For improving power efficiency, during the period where there is no datatransmission to or from the station 100, the station 100 will shut downalmost every components and switch to the sleep mode. In the presentinvention, at least one of the components of the GPIO device 115, thetimer 101, or the retention memory 116 remain awaken when the station100 is operating in the sleep mode. In the sleep mode, the durationbetween two awakenings is referred to as a sleep period. In thisembodiment of the present invention, the GPIO device 115 remainsenabled. The timer 101 and the retention memory 116 are optionallyenabled during the sleep period in another embodiments.

Please refer to FIG. 3 in conjunction to FIG. 2. FIG. 3 is a flowchartof a method of saving power of a station in a wireless network accordingto a first embodiment of the present invention. The method comprises:

Step 300: Upon receiving a wake-up signal, power on the connectivitymodule 140, the timer 101, the retention memory 116, the centralprocessing unit 110, and the peripheral devices 114.

Step 302: Perform the connectivity module 140, the timer 101, theretention memory 116, the central processing unit 110, and theperipheral devices 114 in a connection state and/or in an authenticatedstate.

Step 304: Check whether data from the access point 200 is transferred tothe station 100.

Step 306: Receive the data along with the beacon frames until thestation 100 transmits and receives all needed data.

Step 308: Upon a condition that there is no data to be transferred tothe station or after the station transmits and receives all needed data,perform a sleep mode to power off the connectivity module 140, the timer101, the retention memory 116, the central processing unit 110, and theperipheral devices 114.

In step 300, the GPIO device 115 generates a wake up signal in responseto an external event. When receiving the wake up signal, the battery 130supplies power to power on the connectivity module 140, the timer 101,the retention memory 116, the central processing unit 110, and theperipheral devices 114. In this moment, the central processing unit 110performs cold booting to initialize the connectivity module 140, thetimer 101, the retention memory 116, and the peripheral devices 114.

Referring to FIGS. 3-5, FIG. 4 illustrates a variety of power supply tothe station of the present invention, and FIG. 5 illustrates acomparison of sleep/wake up modes between conventional technology andthe present invention. As shown in FIG. 5, the access point 200 shalltransmit a Traffic Indication Map (TIM) with every beacon, and for everyDelivery Traffic Indication Message (DTIM) period, a TIM of type “DTIM”is transmitted within a beacon. The TIM in a given beacon indicates tothe station 100 whether there is pending unicast traffic for thatstation 100 in the upcoming beacon interval. The DTIM is a bitmap thatindicates whether broadcast and multicast traffic is being delivered inthe upcoming beacon interval. The DTIM is sent at an interval that isselected by the access point 200. The DTIM interval is typicallymultiple times the beacon interval and is fixed for a Basic Service Set(BSS), which is a network of stations associated to the access point200.

Upon the connectivity module 140, CPU 110, and the peripheral devices114 are under a connection state or an authenticated state, (i.e., thestation 100 reconnects the access point 200 or the station 100re-authenticates the access point 200), broadcast frames or multicastframes buffered in the access point 200 are transferred to the station100 along with DTIM. Then, the station 100 can detect whether there isdata (i.e. buffered broadcast or multicast frames) is transferred alongwith DTIM. The authenticated state indicates that the station 100connects to the access point 200 after an authentication process such aslogging in or keying in a password.

In step 306, in the case that data (i.e. buffered frames) along with theDTIM is transmitted from the access point 200, the station 100 receivesthe data along with the beacon frame. In step 308, if there is no dataalong with DTIM to be transferred from the access point 200, itrepresents that no data is buffered in the access point 200. The station100 performs a sleep mode to power off the connectivity module 140, thetimer 101, the retention memory 116, the central processing unit 110,and the peripheral devices 114.

Please refer to FIG. 5. Before receiving a TIM or DTIM, the traditionalstation enables and supplies power from the battery to the elements tobe ready for receiving buffered frames in the access points. Bycontrast, the present invention proposes that a wake up signal is sentfrom the GPIO device 115 in response to an external event. Uponreceiving the wake up signal, the battery 130 supplies power to power onthe connectivity module 140, the timer 101, the central processing unit110, and the peripheral devices 114. Since the interval of the wake upsignal sent from the GPIO device 115 in response to the external eventis a few multiples of the DTIM intervals, the sleep period of theelements in the station 100 according to the present invention is longerthan the conventional DTIM intervals. Therefore, the station using thepresent invention may save more power and thus make the battery lifelonger.

Please refer to FIG. 6 in conjunction to FIG. 2. FIG. 6 is a flowchartof a method of saving power of a station in a wireless network accordingto a second embodiment of the present invention. The method comprises:

Step 600: Upon receiving a wake-up signal, power on the connectivitymodule 140, the retention memory 116, the central processing unit 110,and the peripheral devices 114.

Step 602: Perform the connectivity module 140, the retention memory 116,the central processing unit 110, and the peripheral devices 114 in aconnection state and/or in an authenticated state.

Step 604: Check whether data from the access point 200 is transferred tothe station 100.

Step 606: Receive the data within beacon frame.

Step 608: Upon a condition that there is no data to be transferred tothe station or after the station transmits and receives all needed data,perform a sleep mode to power off the connectivity module 140, theretention memory 116, the central processing unit 110, and theperipheral devices 114.

In step 600, the GPIO device 115 generates a wake up signal in responseto an external event, or the timer 101 periodically generates a wake upsignal. The wake-up signal is generated when the timer 101 expires by apredetermined time period such as 5 seconds. The interval of theperiodical wake up signal from the timer 101 is a few multiples of DTIMintervals. For example, the interval of the periodical wake up signalfrom the timer 101 (5 seconds) is 10 times of DTIM intervals (500mili-seconds). When receiving the wake up signal, the battery 130supplies power to power on the connectivity module 140, the retentionmemory 116, the central processing unit 110, and the peripheral devices114. In this moment, the central processing unit 110 performs coldbooting to initialize the connectivity module 140, the retention memory116, and the peripheral devices 114. Differing from the firstembodiment, the timer 101 of the second embodiment enables andperiodically generates the wake up signal during the sleep mode.

Upon the connectivity module 140, CPU 110, and the peripheral devices114 are under a connection state or an authenticated state, (i.e., thestation 100 reconnects the access point 200 or the station 100re-authenticates the access point 200), broadcast frames or multicastframes buffered in the access point 200 are transferred to the station100 along with DTIM. Then, the station 100 can detect whether there isdata (i.e. buffered broadcast or multicast frames) is transferred alongwith DTIM. The authenticated state indicates that the station 100connects to the access point 200 after an authentication process such aslogging in or keying in a password.

In step 606, in the case that data (i.e. buffered frames) along with theDTIM is transmitted from the access point 200, the station 100 receivesthe data along with the beacon frame. In step 608, if there is no dataalong with DTIM to be transferred from the access point 200, itrepresents that no data is buffered in the access point 200. The station100 performs a sleep mode to power off the connectivity module 140, theretention memory 116, the central processing unit 110, and theperipheral devices 114.

Please refer to FIG. 5. Before receiving a TIM or DTIM, the traditionalstation enables and supplies power from the battery to the elements tobe ready for receiving buffered frames in the access points. Bycontrast, the present invention proposes that a wake up signal is sentfrom the GPIO device 115 in response to an external event or isperiodically generated by the timer 101. Upon receiving the wake upsignal, the battery 130 supplies power to power on the connectivitymodule 140, the central processing unit 110, and the peripheral devices114. Since either the interval of the wake up signal sent from the GPIOdevice 115 in response to the external event or the interval of the wakeup signal periodically generated by the timer 101 is a few multiples ofthe DTIM intervals, the sleep period of the elements in the station 100according to the present invention is longer than the conventional DTIMintervals. Therefore, the station using the present invention may savemore power and thus make the battery life longer.

Please refer to FIG. 7 in conjunction to FIG. 2. FIG. 7 is a flowchartof a method of saving power of a station in a wireless network accordingto a third embodiment of the present invention. The method comprises:

Step 700: Upon receiving a wake-up signal, power on the connectivitymodule 140, the central processing unit 110, and the peripheral devices114.

Step 702: Perform the connectivity module 140, the central processingunit 110, and the peripheral devices 114 in a connection state and/or inan authenticated state.

Step 704: Check whether data from the access point 200 is transferred tothe station 100.

Step 706: Receive the data within beacon frame.

Step 708: Upon a condition that there is no data to be transferred tothe station or after the station transmits and receives all needed data,perform a sleep mode to power off the connectivity module 140, thecentral processing unit 110, and the peripheral devices 114.

In step 700, the GPIO device 115 generates a wake up signal in responseto an external event, or the timer 101 periodically generates a wake upsignal. The wake-up signal is generated when the timer 101 expires by apredetermined time period such as 5 seconds. The interval of theperiodical wake up signal from the timer 101 is a few multiples of DTIMintervals. For example, the interval of the periodical wake up signalfrom the timer 101 (5 seconds) is 10 times of DTIM intervals (500mili-seconds). When receiving the wake up signal, the battery 130supplies power to power on the connectivity module 140, the centralprocessing unit 110, and the peripheral devices 114. In this moment, thecentral processing unit 110 performs cold booting to initialize theconnectivity module 140, and the peripheral devices 114. In anothercase, the central processing unit 110 performs warm booting to read therelevant information from the retention memory 116 relating toassociated states of the central processing unit 110 and the peripheraldevices 114, and relating to authenticated states of the connectivitymodule 140 in a previous operation occurred before the last sleep mode.In this way, the station 100 rapidly recovers to the associated andauthenticated states the same as before the last sleep by restoring therelevant information from the retention memory 116 without performing anew association process and a new authentication process to the accesspoint 200 or another station. Differing from the first embodiment,during the sleep mode, the timer 101 of the third embodiment enables andperiodically generates the wake up signal, or the retention memory 116stores relevant information relating to associated states of the centralprocessing unit 110 and the peripheral devices 114, and relating toauthenticated states of the connectivity module 140 in a previousoperation occurred before the last sleep mode.

Upon the connectivity module 140, CPU 110, and the peripheral devices114 are under a connection state or an authenticated state, (i.e., thestation 100 reconnects the access point 200 or the station 100re-authenticates the access point 200), broadcast frames or multicastframes buffered in the access point 200 are transferred to the station100 along with DTIM. Then, the station 100 can detect whether there isdata (i.e. buffered broadcast or multicast frames) is transferred alongwith DTIM. The authenticated state indicates that the station 100connects to the access point 200 after an authentication process such aslogging in or keying in a password.

In step 706, in the case that data (i.e. buffered frames) along with theDTIM is transmitted from the access point 200, the station 100 receivesthe data along with the beacon frame. In step 708, if there is no dataalong with DTIM to be transferred from the access point 200, itrepresents that no data is buffered in the access point 200. The station100 performs a sleep mode to power off the connectivity module 140, thecentral processing unit 110, and the peripheral devices 114.

Please refer to FIG. 5. Before receiving a TIM or DTIM, the traditionalstation enables and supplies power from the battery to the elements tobe ready for receiving buffered frames in the access points. Bycontrast, the present invention proposes that a wake up signal is sentfrom the GPIO device 115 in response to an external event or isperiodically generated by the timer 101. Upon receiving the wake upsignal, the battery 130 supplies power to power on the connectivitymodule 140, the central processing unit 110, and the peripheral devices114. Since either the interval of the wake up signal sent from the GPIOdevice 115 in response to the external event or the interval of the wakeup signal periodically generated by the timer 101 is a few multiples ofthe DTIM intervals, the sleep period of the elements in the station 100according to the present invention is longer than the conventional DTIMintervals. Therefore, the station using the present invention may savemore power and thus make the battery life longer.

The method of saving power of the station in the wireless networkdescribed herein may be implemented by various means. For example, thesetechniques may be implemented in hardware, firmware, software, or acombination thereof. For a hardware implementation, the processing unitsused to perform the techniques at a station may be implemented withinone or more application specific integrated circuits (ASICs), digitalsignal processors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), processors, controllers, micro-controllers, microprocessors,electronic devices, other electronic units designed to perform thefunctions described herein, or a combination thereof. The processingunits used to perform the techniques at an access point may beimplemented within one or more ASICs, DSPs, processors, etc.

For a firmware and/or software implementation, the power savingtechniques may be implemented with modules (e.g., procedures, functions,etc.) that perform the functions described herein. The firmware and/orsoftware codes may be stored in a memory 112 for CPU 110 in FIG. 2 andexecuted by a processor (e.g., CPU 110). The memory may be implementedwithin the processor or external to the processor.

While the present invention has been described in connection with whatis considered the most practical and preferred embodiments, it isunderstood that this invention is not limited to the disclosedembodiments but is intended to cover various arrangements made withoutdeparting from the scope of the broadest interpretation of the appendedclaims.

What is claimed is:
 1. A method of saving power of a station in wirelessnetwork, the method comprising: upon receiving a first wake-up signal,performing data transmission; upon a condition that there is no data tobe transferred to the station, performing a sleep mode; and uponreceiving a second wake-up signal, performing data transmission; whereinan interval between the first and second wake-up signals is longer thanan interval between two delivery traffic indication messages (DTIMs). 2.The method of claim 1, wherein the delivery traffic indication messagesare received from an access point.
 3. The method of claim 1, wherein thestation comprises a general purpose input/output (GPIO) device, and thewake-up signal is sent from the GPIO device in response to an externalevent.
 4. The method of claim 1, wherein the station comprises aconnectivity module, and the method further comprises: upon a conditionthat there is data to be transferred by a delivery traffic indicationmessage (DTIM) from an access point, performing the connectivity modulein an authenticated state.
 5. The method of claim 1 wherein the stationcomprises a timer, and the first and second wake-up signals aregenerated by the timer.
 6. The method of claim 1, wherein the stationcomprises a connectivity module and a retention memory, the retentionmemory is used for storing information relating to authenticated statesof the connectivity module in a previous operation occurred before thelast sleep mode, and the method further comprises: performing theconnectivity module in the authenticated state complying with theprevious operation.
 7. The method of claim 1, wherein the stationcomprises a connectivity module and the connectivity module comprises amodulator/demodulator, a radio frequency (RF) transceiver, ananalog-to-digital converter, a digital-to-analog converter, and a mediaaccess controller.
 8. The method of claim 1, wherein the stationcomprises a connectivity module and the station connects to anotherstation by using WiFi, Bluetooth, Zigbee, and ZWAVE wireless technologyprotocol through the connectivity module.
 9. The method of claim 1,wherein the station comprises a connectivity module, a centralprocessing unit (CPU), and peripheral devices, and the method furthercomprises: upon receiving the first or second wake-up signal, poweringon the connectivity module, the central processing unit, and theperipheral devices.
 10. The method of claim 1, wherein the stationcomprises a connectivity module, a central processing unit (CPU), andperipheral devices, and the method further comprises: upon performingthe sleep mode, powering off the connectivity module, the centralprocessing unit, and the peripheral devices.